Geostress field plays an important role in the stability of tunnel surrounding rock. Based on the in-situ stress results and geological conditions in the cracked area of the secondary lining concrete of the Qinling water conveyance tunnel from Hanjiang-to-Weihe, three-dimensional hydraulic fracturing method was used to analyze the in-situ stress of the surrounding rock in Qinling tunnel. The results show that the maximum principal stress on the cross section of the horizontal hole is 16.3-37.9 MPa and the minimum principal stress on the cross section is 2.4-9.1 MPa in the horizontal drilling depth range of 9.2-26.6 m. In the vertical drilling depth range of 3.8-20.7 m, the maximum horizontal principal stress is mainly 21.5-30.5 MPa, the azimuth average is N57°E, and the minimum horizontal principal stress is mainly 12.7-16.5 MPa. The maximum and minimum and the spatial maximum principal stress are 24.3 MPa, 14.4 MPa and 24.6 MPa respectively, which are nearly horizontal distribution. The stress field of surrounding rock at the test site of tunnel rock mass is mainly horizontal stress and the rock mass stress is classified as "high in-situ stress".

In the long service process of the deep excavated expansive soil channel slope, the real-time identification of the service behavior of the channel slope by means of displacement monitoring index is an important means to ensure the safe operation of the channel slope. Therefore, it is of great significance to formulate reasonable monitoring indexes for the safety of canal slope engineering. The POT model was presented in this paper. On the basis of introduction of 2 σ criteria and chauvenet principles, the threshold T and the corresponding relation between monitoring index was established. Through the best solution to satisfy the relationship between threshold, a canal slope displacement monitoring index for improved POT model was established to apply to the Taocha section of South-to-North Water Transfer Project of deep excavation expansion earth canal in slope engineering. Compared with the traditional POT model, the results show that the improved POT model based on 2σ -chauvenet criterion can effectively avoid subjectivity and random error, and it has higher calculation accuracy. The proposed displacement monitoring index is more safety, which has stronger guiding significance to prevent the risk of canal slope and ensure the safe long-term operation of canal slope.

In view of the difference between the performance of cemented gravel soil under low normal stress and high normal stress, based on the Mohr-Coulomb strength criterion, according to the Mohr-Coulomb strength line of cemented gravel soil before and after yield stress, a polygonal line strength criterion of cemented gravel soil was proposed. The relationship between strength criterion parameters and uniaxial compressive strength and uniaxial tensile strength was deduced. Uniaxial compression test and direct tensile test were carried out to calculate the strength criterion parameters and compare with the strength criterion parameters obtained by triaxial compression test. The results show that the error range between the calculated value and the experimental value is reasonable. The polygonal line strength criterion is suitable for cemented gravel soil.

Aiming at the problem that the reliability calculation results of embankment slope stability are not accurate due to the fact that the correlation between variables cannot be considered in two-dimensional independent distribution, based on 171 sets of test data of the shear strength of the Yangtze River embankment shoreline soil, Copula function was used to study the correlation between the shear strength parameters of the Yangtze River embankment shoreline soil. The AIC and BIC criteria were used to identify the optimal edge distribution and Copula function, and a two-dimensional joint distribution model was constructed. The influence of data volume on the identification of correlation structure between parameters was analyzed. The results show that the two-dimensional joint distribution model based on Copula function can accurately characterize the correlation between soil parameters of the Yangtze River embankment shoreline; When the data volume is more than 24 groups, AIC and BIC criteria can accurately identify the optimal Copula function, which provides a reference for the reliability calculation of embankment slope and the construction of Copula function model.

This study analyzed the mechanism of groundwater gushing from Quaternary boreholes at Aishan section of the lower reaches of the Yellow River in autumn floods. Groundwater level analysis, meteorological analysis, runoff analysis of the Yellow River, combined with isotopic analysis of groundwater and surface water samples were used. The results show that the average groundwater level was increased more than 3 m, which reduced the groundwater runoff. The increase of groundwater level was the basic factor of groundwater gusher. Continuous high water level of the Yellow River and the intensive water replenishment of the Yellow River to groundwater directly led to the groundwater gushing. The warning groundwater level of wells near Aishan section of the lower reaches of the Yellow River was 39.5 m within the 500 m outside the dike. This paper provides a basic understanding for preventing groundwater gushing from wells outside the levee of the Yellow River, and it is helpful for the protection of the levee of the Yellow River.

To avoid flow surface morphology change caused by wear and cavitation erosion of turbine movable guide vane and the unit efficiency decrease, ultrasonic vibration cavitation machine, high-speed jet of gaza's grinding apparatus and circle grinding apparatus were used to carry out cavitation erosion test for epoxy mortar, mortar composite resin and polyurethane and movable guide vane base material of ^#45 steel. Based on the test results, the cavitation erosion resistance and impact wear resistance of different materials were analyzed, and the service life of materials under strong cavitation erosion was predicted. The influence of flow rate, attack angle and sand content on material wear was studied, and the prediction model of material wear was established. The results show that the corrosion resistance of the materials is as follows: polyurethane > composite resin mortar > epoxy mortar; The abrasion loss of material has a linear or exponential relationship with the increase of velocity. The relationship between wear and sand content is linear. When the attack angle increases gradually, the impact wear first reaches the peak value and then decreases gradually. The critical attack angle of different materials is different.

For the 1# bulb tubular unit of Baisha Hydropower Station, the prestress vanishment of the rotor bracket and hot sleeve of the spindle could results the scratching of the generator and the uneven air gap between stater and rotor, which generates the excessive unilateral magnetic pull. This problem may lead to a serious accident in runaway or load rejection conditions. According to the experiential and theoretical analysis, the solution points to the fastening connection by a pin arrangement between rotor bracket and main shaft. Consequently, the unit has been running steadily under various working conditions. As there are numerous large, medium and small units in China facing the similar problem, the treatment scheme and design calculation methods proposed in this paper could be considered as a typical solution reference.

In order to solve the heat dissipation problem of heat pipe rectifier cabinet for excitation system of giant hydropower station, the working principle of loop heat pipe and the processes of development and improvement of loop heat pipe rectifier cabinet were introduced. The advantages of integrated loop heat pipe and horizontal symmetry structure, as well as its application in Wudongde Hydropower Station were analyzed. The practice shows the loop heat pipe rectifier cabinet adopting completely self-cooling heat dissipation mode is in a thermal stable state after long-term operation in the field, and a series of problems, such as dust, noise, power supply, maintenance, can be solved from the design principle. Meanwhile, it can improve the safety, reliability and automation level of the equipment and reduce the energy consumption, the benefits of energy-saving and environmental protection are obvious.

Using the daily meteorological dataset of basic meteorological elements of China National Surface Weather Station (V3.0) as a control, the reproducibility of the spatial and temporal distribution characteristics of hourly precipitation in North China during the warm season (June-September) by the China Hourly Merged Precipitation Analysis (CHMPA) and the CPC MORPHing technique (CMORPH) were compared and analyzed. The hourly precipitation and daily variation characteristics of the warm season in North China were further investigated. Results show that the spatial and temporal distribution of precipitation in CHMPA and CMORPH during 2008-2018 is basically consistent with the observation, the estimation of precipitation by CHMPA is generally smaller than the observation, while CMORPH is larger than the observation. The CHMPA data has high spatial resolution and little difference with the actual observation, which is more conducive to the diagnosis analysis of strong convective weather. The overall warm season hourly precipitation in North China is characterized by more precipitation in the southeast and less in the northwest, with normal rain mostly occurring in the plateau area and flash heavy rain mostly occurring in the transition area between the plateau and the plain and the plain area. The warm season precipitation in North China has obvious daily variation characteristics. The large value of precipitation center appears in the afternoon near the mountains, then gradually moves southeast and causes large precipitation in the western part of the North China Plain at night, and the precipitation center reaches the central part of the plain in the early morning of the next day. The precipitation gradually weakened in North China from early morning to noon the next day. The peak of precipitation and precipitation frequency occurs mostly from midday to late afternoon in the plateau area and from midnight to early morning in the plain area. The results provide a theoretical reference for precipitation research and forecast in North China.

To analyze the applicability of CMORPH merged hourly gridded precipitation product in Northern China, the statistical indicators between the observed grid precipitation and CMORPH merged gridded precipitation in temporal and spatial distribution of flood season from 2008 to 2012 were evaluated in the Yihe River Basin. Using the two precipitations as the input of HEC-HMS model, the feasibility of floods forecast of the CMORPH merged precipitation was evaluated. The results show that the CMORPH merged precipitation has a high correlation with the observed grid precipitation, and the flood simulation accuracy is comparable to the result of observed grid precipitation, and performing better in the simulations both runoff volume and flood peak. The satellite merged precipitation has good applicability in flood forecasting in the study area.